1. Field of the Invention
The invention generally relates to matched filters and, in particular, to dedicated message matched filters.
2. Description of the Prior Art
Audio or other information may be encoded on a spread spectrum waveform by periodically sampling and coding the information and modulating it on the waveform. In order to recover the original audio modulation samples, a matched filter for each code sequence is required that retains the code corresponding to a time interval equal to the transit time for an emitter at maximum range. The number of matched filters needed to process emitters anywhere within the total range interval is equal to the transit time at maximum range divided by the duration of one code subinterval. For example, a system with a maximum range of 200 miles and a code interval of 60 microseconds would require 20 matched filters if a conventional processor is employed. The purpose of this invention is to reduce the number of matched filters necessary to recover the original information.